Glasses, astigmatism eyepieces option

[heliumstar]

So, astigmatism got a little worse and I got new prescription for glasses. I am thinking of going full 20mm+ eye relief with all eyepieces and just wear glasses when observing.

So far I found Pentax XW (had them and they are great but oh my the size), Baader Morpheus (size is again an issue but great eyepieces) and TV Delite.

Is there anything out there in the range of 15-5mm with small form factor and eye relief ok with glasses that I am missing?

[Ruud]

For any given eye relief, with a larger apparent field of view you need a larger eye lens, and with a larger eye lens you get a bigger eyepiece.

On top of that, large eye relief eyepieces often get longer with decreasing focal length. That is because they require a stronger first, negative group.

---

The Delites are petite, the Morpheus are lightweight and the Delos are heavy. You found the XW. There's also Nagler type 4. That's about it for the top shelf long eye relief choices.

[Carbon Brush]

Presumably you have ruled out contact lenses to correct the atigmatism?

For me, that is the preferred choice.
They work well and allow me to have a free choice on eyepiece types.

HTH, David.

[Louis D]

The Vixen SLV range have long eye relief and a reasonable form factor, though only a 50 degree field of view.

The Meade 5000 HD-60 also have long enough eye relief to use with eyeglasses and are slightly smaller than the XW and Morpheus.

Make sure to get a pair of single vision, distance only eyeglasses for astro work if you have presbyopia as well as astigmatism since you want the entire field of view at the same focus distance.  Since it is next to impossible to get glass lenses, the next best is low index plastic to avoid the off axis chromatic aberration of high index lenses.

[heliumstar]

Thanks for posts everyone. I own or owned XW, SLV, Morpheus and liked them all. Time to try Delite?

My prescription for astigmatism is Cyl Right -1.25, Cyl Left -1.5 and Axis Right 170, Axis Left 5. Realistically do I need glasses when observing> I don't use eyepieces with more than 2.5mm exit pupil at the moment as I am mostly after double stars and planets and observe deep space with camera.

Edited February 27, 2020 by heliumstar
less=more

[Louis D]

22 minutes ago, heliumstar said:

Thanks for posts everyone. I own or owned XW, SLV, Morpheus and liked them all. Time to try Delite?

My prescription for astigmatism is Cyl Right -1.25, Cyl Left -1.5 and Axis Right 170, Axis Left 5. Realistically do I need glasses when observing> I don't use eyepieces with less than 2.5mm exit pupil at the moment as I am mostly after double stars and planets and observe deep space with camera.

According to Tele Vue, astigmatism in your case is likely to be noticeable in exit pupils above 1.5mm:

Thus, you might want correction between 1.5mm and 2.5mm.  I assume you meant "more than 2.5mm exit pupil" above since most double star and planet observation is done at small exit pupils.

I have 2 diopters of astigmatism in my observing eye, and I can see it at 1mm, and somewhat below that as well, though it is subtle.  If you use a driven mount and only observe small objects like double stars and planets on axis, you can probably get away with shorter relief eyepieces and just back off from the eyepiece while wearing eyeglasses.  Compare the views with and without glasses to determine for yourself your astigmatism tolerance threshold.

[heliumstar]

Thanks for this Louis. Yep, meant more than 2.5mm exit pupil.

[Don Pensack]

On 27/02/2020 at 04:25, heliumstar said:

So, astigmatism got a little worse and I got new prescription for glasses. I am thinking of going full 20mm+ eye relief with all eyepieces and just wear glasses when observing.

So far I found Pentax XW (had them and they are great but oh my the size), Baader Morpheus (size is again an issue but great eyepieces) and TV Delite.

Is there anything out there in the range of 15-5mm with small form factor and eye relief ok with glasses that I am missing?

Baader Hyperion, Baader Morpheus, Explore Scientific 92° series, Explore Scientific 28,34,40 x 68°, ES 26,32, 40 x 62°, ES 30, 40 x 52°, TeleVue Nagler 31, Delos eyepieces, Delite eyepieces, Nagler 22,

Olivon 70° series, Olivon 58° series, Vixen SLV, Pentax XW, APM UFF in 24mm and 30mm

Boiling it down to the 5-15mm range, 2 Hyperions, 4 Morpheus, 7 Delos, 8 Delites, 3 Olivon 70, 6 Olivon 58s, 5 Pentax XW, 2 Pentax XF, 8 Vixen SLV = 45 eyepieces in your range,

and that's not all of them, merely the ones I can remember off the top of my head.

But, bear in mind you may not need glasses below a certain exit pupil.  I use glasses from 11mm up and no glasses for 10mm down.  You may not require glasses for your shortest focal lengths.

[heliumstar]

Thanks @Don Pensack for a comprehensive answer. Those Pentax XF look very slim and I have had my eye on them for quite some time now! I would go all Delites but posts on CN about Delites giving washed out star colours in comparison to other eyepieces in small scopes (and my main visual now is 60mm) made me look into other direction.

I realise now that I may be a little too quick to just throw out the idea of eyepieces with less than 20mm eye relief. Looks like under 15mm it should be perfectly fine but I was told astigmatism will get worse so maybe plan for that as well.

 

[Don Pensack]

My astigmatism has gotten worse over the years.  At first, no visible astigmatism at 6mm exit pupil, then 4mm, then 2mm.

But the eyepieces I use under the 2mm exit pupil are so good, I don't intend to part with them until forced to do so by Mother Nature.

You can plan for getting worse, I suppose, and just get only eyepieces compatible with glasses all the way down to the smallest focal length.

I can see that, but I'd hate to give up 100-120° fields, especially at high power in an undriven dob.

[Merlin]

I wear specs. I solved the problem of getting eye relief with shorter focus eyepieces by sawing and filing down a pair of spare specs lenses, then, I fitted them into the eyepiece sockets with blue tack. It works well.

[Louis D]

3 hours ago, heliumstar said:

Those Pentax XF look very slim and I have had my eye on them for quite some time now!

The reports of the 12mm Pentax XF having quite a bit of field curvature are true.  I picked one up when Amazon had them half off, and I'm still not convinced it was worth it.  Below are my 12mm eyepiece comparison images.  Notice how the Pentax is fuzzy at the edge while the HD-60 and Paradigm are not.  Refocused, the XF sharpens up considerable.

Edited March 11, 2020 by Louis D